A known electrowetting display device includes two support plates. A pattern of walls is arranged on one of the support plates, the pattern defining the picture elements of the display device. The area between the walls of a picture element, also known as a pixel, is called the display region, over which a display effect occurs. The walls of the picture elements are made of a hydrophilic material. The area of the support plate in the display region must to a large extent be hydrophobic for a proper operation of the picture element. During manufacture the area of the support plate where the picture elements are located is covered by a hydrophobic layer. The walls are made on this layer by depositing a layer of wall material on the hydrophobic layer and patterning the layer of wall material using e.g. a photo-lithographic method.
The adhesion between the layer of wall material and the hydrophobic layer is relatively poor, causing easy peel off of the layer of wall material from the hydrophobic layer. It is known to lower the hydrophobicity of the hydrophobic layer prior to applying the layer of wall material. After the formation of the walls, the area of the hydrophobic layer between the walls is annealed to regain its hydrophobicity. However, the quality of display devices made using this method is not satisfactory.